Different versions of Christianity have different standards a person must meet in order to be called a Christian. A Roman Catholic, for example, may define a Christian as someone who attends mass and participates in the sacraments. However, even the most ardent Catholic probably doesn’t believe their Lutheran neighbor is invariably consigned to the pits of hell. As an evangelical, I hold that everyone who has a personal relationship with God through the death, burial, and resurrection of Christ are Christians regardless of their denomination. Thus, I believe that there are real and phony Christians in the Southern Baptist Convention, the Roman Catholic Church, and the United Methodist Church.

However, some religious groups claim to have a saving faith in Christ while also holding beliefs that are antithetical to Christian belief. Mormons, for example, claim to be Christians; indeed, they claim to be the only Christians. However, Mormonism’s versions of several essential doctrines, such as the person of the Father, the identity of Jesus, the nature of the atonement, and Christ’s resurrection, are heretical according to scripture. To be blunt, it’s hard to see how a person could be a Christian and hold to some of these beliefs. Perhaps I’m wrong; however, if I’m wrong, it’s because I’ve followed what the Bible teaches too closely. From my reading of scripture, I hold that some beliefs are incompatible with Christianity. There are things that a person simply must believe or they cannot be a born-again Christian.

Evangelicals often say that anyone who has a saving faith in Christ is a Christian regardless of where they go to church. However, at the same time, we say that there are certain beliefs that a person must affirm to be a believer. Consequently, if a person accepts the beliefs of a group—religious or otherwise—that rejects these essential doctrines of Christianity, that person cannot be a Christian. Accordingly, if a person is a born-again Christian and a Mormon, they must be a poor Mormon. To put it another way, there is a certain body of beliefs that a person must affirm in order to be a Christian.

What exactly is in this essence of Christianity? What are these beliefs that a person must hold in order to be an authentic Christian?

The historic creeds were efforts to delineate these basic beliefs; however, it seems that they go too far sometimes. Orthodox Christians, like myself, will affirm the Nicene Creed. However, if a person doesn’t accept the doctrine of the Trinity and thus rejects the Nicene Creed, I find myself hesitant to label that person a non-believer. I believe their theology is in serious error; however, I don’t think they’ve apostatized. Thus, I want to go past the affirmations of the historic creeds until I hit something more foundational. What I’m saying is that orthodoxy is not identical to Christianity.

So, what is essential, minimalistic Christian belief? What constitutes the mere Christianity that C.S. Lewis so famously discussed? What doctrines serve as the basic underpinnings of all confessions of faith and creeds?